Cochlear stimulation systems commonly comprise a cochlear implant, which includes an implantable sealed metal housing containing stimulation circuitry connected by metal feedthrough pins to an implantable cochlear electrode. While failures in such systems are relatively rare, when they occur they are often traced to the stimulation circuitry contained within the sealed metal housing. Such failures require a surgical removal and replacement of the cochlear implant.
After such removal, the sealed metal housing is opened and the stimulation circuitry examined to locate the failure and to determine the mechanism that caused the failure. One such failure mechanism is corrosion of or other damage to stimulation circuit components due the collection of ion-containing moisture within the sealed metal housing. Such moisture may be released by the circuitry materials and/or moisture that has leaked into the housing. One avenue for such moisture leakage into the housing has been found to be the insulating seals for the metal feedthrough pins connecting the stimulation circuitry to the cochlear electrode. Glass seals are commonly employed to hermetically seal and insulate the feedthrough pins in the metal housing. They have been found to be subject to cracking around the feedthrough pins when subjected to excessive forces during assembly, testing, or use of the stimulation circuitry.
Whatever the moisture source, it is important that it be eliminated or controlled so that ion-carrying moisture does not collect within the sealed metal housing of a cochlear implant in sufficient quantities as to produce an operational failure within its associated cochlear stimulation system. After extensive research and development, applicant and his associates have developed a system and method of assembly for controlling the collection of moisture within the metal housing of cochlear stimulation systems that will extend the potential reliable operational life of cochlear implants to more than 60 years.